1. Field of the Invention
The present invention relates a method of manufacturing a vane.
2. Description of the Related Art
An oil-sealed rotary vacuum pump of a rotary blade type has been used in which an exhausting operation is carried out by a compressing operation using a plurality of vanes. The oil-sealed rotary vacuum pump includes a rotor rotating in the inside of a cylinder and a vane protruding from the rotor toward the cylinder. The vane of the oil-sealed rotary vacuum pump has a function of dividing a compressing space, and is formed of a resin material such as thermosetting resin (for example, see Japanese Unexamined Patent Application, First Publication No. 2006-328215 and Japanese Unexamined Patent Application. First Publication No. 2005-272652).
FIG. 5 is a flow diagram showing a method of manufacturing the vane according to the related art. The method of manufacturing the vane according to the related art includes a base material forming process (a) of forming a base material 131 (FIG. 5A); a crude processing process (b) of forming a crude product 132 from the base material 131 (FIG. 5B); a drying or heat-treating process (c) of drying or heat-treating the crude product 132 by a heater 146 (FIG. 5C); a finishing process (d) of finishing the crude product 132 to obtain a final product 130 (FIG. 5D); a storing process (e) of storing the final product 130 while preventing moisture absorption using a dryer 152 (FIG. 5E); and an oil impregnating process (f) of immersing the final product 130 into oil 190 used for the oil-sealed rotary vacuum pump (FIG. 5F).
The oil-sealed rotary vacuum pump generates heat by the compressing operation during the operation thereof. Accordingly, an uncured portion of the thermosetting resin forming the vane may be cured to thereby shrink the vane. When the vane shrinks to thereby increase a gap between the vane and the cylinder, an ultimate pressure increases, so that an exhausting speed decreases and a noise level increases.
Therefore, the heat-treating process (FIG. 5C) of the method of manufacturing the vane according to the related art is carried out at a temperature higher than a temperature of the vane upon running the oil-sealed rotary vacuum pump.
A pressure in the vicinity of the vane is approximately equal to a vacuum state upon running the oil-sealed rotary vacuum pump. However, in the method of manufacturing the vane according to the related art, the heat-treating process (FIG. 5C) is carried out at the atmospheric pressure. When the heat-treating process is carried out at the atmospheric pressure, since a curing speed of the thermosetting resin is slower than that in the heat-treating process in the vacuum state, it is not possible to completely cure the uncured portion of the thermosetting resin. For this reason, the curing of the resin material further progresses upon running the oil-sealed rotary vacuum pump, thereby causing a problem of shrinking deformation of the vane.
Furthermore, since the heat-treating process (FIG. 5C) is carried out at the atmospheric pressure, it is difficult to completely separate a low vapor pressure component contained in the material of the vane. For this reason, the low vapor pressure component is separated from the vane upon running the oil-sealed rotary vacuum pump, thereby causing a problem of shrinkage deformation of the vane.
Furthermore, even when the low vapor pressure component is completely removed by carrying out the heat-treating process (FIG. 5C) at a high temperature, moisture contained in the atmosphere enters space formed by the removal (moisture absorption), thereby causing dilation deformation of the vane before the finishing process (FIG. 5D). For this reason, the moisture is separated from the vane upon running the oil-sealed rotary vacuum pump, thereby causing a problem of shrinkage deformation of the vane.